Control system for synchronous capacitor switch

ABSTRACT

Systems and methods for connecting a power source to switched capacitors are provided. A method may be used in controlling the connection of a multiple phase power source to a plurality of capacitors. Each phase of the multiple phase power source is electrically connectable to at least one of the capacitors through a switching device. The method comprises, for each phase of the multiple phase power source, determining a first voltage of a power signal for the respective phase of the power source using a first voltage divider that is electrically connected to a first terminal of the switching device for the phase. The method further comprises determining a second voltage across a capacitor that is connected to a second terminal of the switching device for the phase. The second voltage is determined using a second voltage divider that is connected to the second terminal of the switching device.

BACKGROUND

The present disclosure relates generally to the field of electricalswitch control systems. More specifically, the present disclosurerelates to systems and methods for controlling a switch to selectivelyconnect a power source (e.g., a three phase, medium voltage powersource) to one or more capacitors.

Switched capacitor banks are installed on poles and at sub stations toapply power factor correction (e.g., by altering the load phasing) tothe power grid in response to the application and removal of heavyindustrial inductive loads such as motors. When loads are not in phase,additional reactive currents increase transmission losses which resultsin wasted energy and the need for additional generating capacity. Insome systems, a separate control senses the voltage-to-current phaserelationship and commands the capacitor switch to open and close basedon the relationship. Applying capacitors may help improve the transferefficiency of the electrical energy being transmitted through the powergrid. Medium voltage applications (e.g., 5 kV-38 kV) often includecapacitors that are switched on and off based on power factor correctionneeds.

If a switch closes at a time when the AC voltage across the switch isnot at a waveform zero, disturbances may occur due to heavy inrushcurrents as the capacitors are charged. The disturbances may include,for example, voltage dips, harmonics, resonance peaks and/or otherundesirable effects on the electrical system. Such disturbances cancause problems with sensitive customer equipment, such as industrial VFD(variable frequency drive) motor controllers. Due to the mechanical andelectrical complexity, the majority of medium voltage capacitor switchesclose randomly with respect to voltage. Some systems are configured witha resistor inserted in series with the switch to charge the capacitor tovoltage, reducing the inrush current. Such systems may be acceptable forsome applications, but may not perform in an acceptable fashion for moresensitive applications.

Controllers that are configured to close when the voltage across thecapacitor switch is nearly zero volts are typically complex, expensive,and difficult to commission/install because they must handle a complexmixture of mechanical and electrical variations. Complex algorithms maybe used to estimate the voltage across each switch, and such algorithmsmay require the installer to provide detailed information about theinstallation, such as the phase rotation (e.g., A-B-C phasing or A-C-Bphasing), Wye/Delta capacitor connections and capacitor grounding (e.g.,grounded or ungrounded). Some controllers blindly time their operationsbased on a single phase voltage sensor and calibration informationregarding the electrical system to which the system is connected. Forexample, a voltage sensing transformer may reference only phase A of athree phase system. If the capacitor bank is connected in a grounded Wyeconfiguration, it is expected that the electrical timing between zerovolts of each phase is separated by 120 electrical degrees. The phaserotation must be known to configure such a controller.

Additionally, conventional zero-closing switches are configured tomeasure voltage on a single side of the switch (e.g., the power sourceside). When a Medium Voltage AC switch operating a capacitor opens, thecurrent is cleared at a zero crossing. Since the current and voltagesignals are out of phase 90 degrees due to the capacitor, a near peaktrapped DC charge is left on the capacitor after the switch is opened.Capacitors have an internal resistor that is configured to slowlydissipate this energy until the voltage across the capacitor is broughtto zero volts. In order to ensure that the capacitor has fullydischarged (e.g,. such that the voltage on the capacitor side of theswitch is zero) and that closing the switch will not induce abnormallylarge inrush current (e.g., more than 6 times load capacitive loadcurrent), conventional zero-closing switches may be configured to wait apredetermined amount of time (e.g., five minutes) after the switch waslast opened before closing the switch again. Closing the switch prior tothe predetermined amount of time may produce an abnormally large inrushcurrent (e.g., up to 80 times load current) as the source voltage meetsa large trapped charge voltage on the capacitor. Specializedinterlocking control equipment, training, and/or signage is often usedto prevent closing of the switch prior to the passage of thepredetermined amount of time.

There is a need for an improved control system for controlling theoperation of switches used to selectively connect power sources toswitched capacitors. There is also a need for a control system that ishighly repeatable under a variety of environmental conditions. Further,there is a need for a control system that can be connected to a varietyof different power system and/or capacitor configurations without theneed for a substantial amount of specialized calibration to theindividual types of configurations. Further still, there is a need for acontrol system that provides greater knowledge and awareness of thevoltage conditions on both sides of the switch. There is also a need fora control system that does not require the switch to wait apredetermined amount of time after opening before the switch may closeagain.

SUMMARY

One exemplary embodiment of the disclosure relates to a method ofcontrolling the connection of a multiple phase power source to aplurality of capacitors. Each phase of the multiple phase power sourceis electrically connectable to at least one of the plurality ofcapacitors through a switching device. The method comprises, for eachphase of the multiple phase power source, determining a first voltage ofa power signal for the respective phase of the power source using afirst voltage divider that is electrically connected to a first terminalof the switching device for the phase. The method further comprises, foreach phase, determining a second voltage across a capacitor that iselectrically connected to a second terminal of the switching device forthe phase. The second voltage is determined using a second voltagedivider that is electrically connected to the second terminal of theswitching device for the phase. The method further comprises, for eachphase, generating a close signal configured to cause the switchingdevice for the phase to close and electrically connect the respectivephase of the power source to the capacitor when the difference betweenthe first voltage and the second voltage is approximately zero.

Another exemplary embodiment of the disclosure relates to a controlsystem for controlling the connection of a multiple phase power sourceto a plurality of capacitors. Each phase of the multiple phase powersource is electrically connectable to at least one of the plurality ofcapacitors through a switching device. The control system comprises acontrol circuit. The control circuit is configured to, for each phase ofthe multiple phase power source, determine a first voltage of a powersignal for the respective phase of the power source using a firstvoltage divider that is electrically connected to a first terminal ofthe switching device for the phase. The control circuit is furtherconfigured to, for each phase, determine a second voltage across acapacitor that is electrically connected to a second terminal of theswitching device for the phase. The second voltage is determined using asecond voltage divider that is electrically connected to the secondterminal of the switching device for the phase. The control circuit isfurther configured to, for each phase, generate a close signalconfigured to cause the switching device for the phase to close andelectrically connect the respective phase of the power source to thecapacitor when the difference between the first voltage and the secondvoltage is approximately zero.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a control system that may be used tocontrol the operation of switching devices for selectively connecting athree phase voltage source to switched capacitors according to anexemplary embodiment.

FIG. 2 is a single-phase block diagram of the control system shown inFIG. 1 according to an exemplary embodiment.

FIG. 3 is a flow diagram for a process of controlling the operation of aswitching device for connecting a voltage source to a switched capacitoraccording to an exemplary embodiment.

FIG. 4 is a single-phase schematic electrical diagram of a controlsystem for controlling the operation of a switching device forconnecting a voltage source to a switched capacitor according to anexemplary embodiment.

FIG. 5 is a perspective view of a control system that may be used tocontrol the operation of switching devices for selectively connecting athree phase voltage source to switched capacitors according to anexemplary embodiment.

FIG. 6 is a back planar view of the control system of FIG. 5 accordingto an exemplary embodiment.

FIG. 7 is a perspective view of a lateral cross-section of the controlsystem shown in FIG. 5 according to an exemplary embodiment.

FIG. 8 is a front planar view of a lateral cross-section of the controlsystem shown in FIG. 5 according to an exemplary embodiment.

FIG. 9 is a front planar view of a switching device that may be used toconnect and/or disconnect a voltage source to a switched capacitoraccording to an exemplary embodiment.

FIG. 10 is a rear planar view of the switching device of FIG. 9according to an exemplary embodiment.

FIG. 11 is a schematic illustration of an operating rod that may be usedin connecting and/or disconnecting a voltage source to a switchedcapacitor according to an exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the Figures, it should be noted that references to“front,” “back,” “rear,” “upward,” “downward,” “inner,” “outer,”“right,” “left,” and/or other directional terms in this description aremerely used to identify the various elements as they are oriented in theFigures. These terms are not meant to limit the element which theydescribe, as the various elements may be oriented differently in variousapplications.

Referring generally to the Figures, systems and methods for controllingthe connection between a power source, such as a multiple-phase (e.g.,three phase) power source, and one or more capacitors are providedaccording to various exemplary embodiments. A switch system may becomprised of a separate switching device or contactor for each phase ofa multiple-phase system (e.g., three contactors for three phases). Invarious embodiments, for each phase, separate voltage dividers may beprovided on each side of the switching device (e.g., one on thecapacitor or load side, another on the power source or grid side). Thevoltage dividers may be used to determine the voltage on each side ofthe switching device for the phase. A control circuit may compare thedetermined voltages to decide if and when the voltage across the switch(e.g., the difference between the voltages on the opposite sides of theswitch) is approaching approximately zero. The control circuit may thengenerate a signal (e.g., a close signal) that may be transmitted to theswitching device to cause the switching device to close and form anelectrical connection between the power source and the one or morecapacitors at about the time when the difference in the voltagesapproaches approximately zero volts.

In various exemplary embodiments (e.g., systems and/or methods), variousfeatures may be utilized to control the connection between a powersource and switched capacitors. For example, a close signal may begenerated before the capacitor is fully discharged. The close signal maybe generated a predetermined time prior to when the difference betweenthe first voltage and the second voltage is expected to approachapproximately zero. The predetermined time may be based on a time delaybetween a time when the switching device receives the close signal and atime when the switching device comes to rest in a closed position. Thetime delay may be determined by applying a voltage across the first andsecond terminals of the switching device at a first time, closing theswitching device, and determining a second time at which the voltageapproaches approximately zero, wherein the time delay comprises thedifference between the first time and the second time.

A power supply may be provided that is configured to provide anapproximately constant current to power the switching device.

The switching device may comprise a rod configured to be moved between afirst position in which the switching device is in an open position anda second position in which the switching device is in a closed position.At least a portion of the first voltage divider or second voltagedivider may be positioned within the rod. The voltage divider positionedwithin the rod may include one or more high voltage thick filmresistors. The resistor(s) may be encapsulated within a urethanematerial.

Referring now to FIG. 1, a block diagram of a control system 100 thatmay be used to control the operation of switching devices forselectively connecting a three phase voltage source to switchedcapacitors is shown according to an exemplary embodiment. System 100 maybe used to control the time at which three switching devices 160, 165,and 170 (e.g., one for each of the three phases of the power source) ofa three phase switching system close and form an electrical connectionbetween the power source and the capacitors. While system 100 isillustrated as being applied to a three phase system, the features ofsystem 100 described herein may be applied to any single-phase ormultiple-phase power system.

System 100 includes a control circuit 105 configured to receive inputsignals from voltage dividers and generate control signals forcontrolling the operation of switching devices based on the inputsignals. In some embodiments, control circuit 105 includes a processor110 and a memory 115. Processor 110 may be any type of general orspecial purpose processing circuit or device. Memory 115 may be any typeof machine-readable medium, such as flash memory, RAM, ROM, etc.

Memory 115 may include one or more modules configured to perform variousfunctions of control circuit 105. For example, memory 115 may include avoltage comparator module 120 configured to compare voltages receivedfrom voltage dividers and determine when the difference between thevoltages is approaching approximately zero. Memory 115 may additionallyor alternatively include a switch control module configured to generatesignals (e.g., close and/or open signals) configured to instruct theswitching devices to open or close. In some embodiments, the modules maybe implemented using machine-executable instructions stored in memory115 and executable by processor 105. In some embodiments, some or all ofthe functions of control circuit 105 such as comparing input voltagesand/or sending control signals to switching devices, may be implementedusing circuitry other than a processor and/or memory.

Control circuit 105 is configured to receive voltage signals from atleast two voltage dividers for each phase of the multiple-phase powersystem. As illustrated, control circuit receives a voltage input signalfrom a first voltage divider 130 for phase A (e.g., a power source-sidevoltage divider for phase A), a second voltage divider 135 for phase A(e.g., a capacitor or load-side voltage divider for phase A), a firstvoltage divider 140 for phase B (e.g., a power source-side voltagedivider for phase B), a second voltage divider 145 for phase B (e.g., acapacitor or load-side voltage divider for phase B), a first voltagedivider 150 for phase C (e.g., a power source-side voltage divider forphase C), and a second voltage divider 155 for phase C (e.g., acapacitor or load-side voltage divider for phase C). In someembodiments, a low voltage terminal or lead of each of the voltagedividers and/or of control circuit 105 may be connected to the same lowvoltage reference or ground terminal.

Control circuit 105 is configured to generate signals for transmissionto phase A switching device 160, phase B switching device 165, and phaseC switching device 170 based on the voltage inputs from the respectivephase voltage dividers. For example, control circuit 105 is configuredto generate control signals for phase A switching device 160 based onthe voltage inputs from voltage dividers 130 and 135, to generatecontrol signals for phase B switching device 165 based on the voltageinputs from voltage dividers 140 and 145, and to generate controlsignals for phase C switching device 170 based on voltage inputs fromvoltage dividers 150 and 155. In some embodiments, a single controlcircuit may be used to control the operation of switching devices forall phases. In other embodiments, multiple control circuits (e.g., acontrol circuit for each phase) may be utilized to control the operationof the switching devices.

Referring now to FIG. 2, a block diagram of single-phase system 200 ofcontrol system 100 that is illustrated in FIG. 1 is shown according toan exemplary embodiment. Single-phase system 200 illustrates theoperation of control circuit 105 in controlling the connection of asingle phase A to one or more capacitors using phase A switching device160. Control circuit 105 is configured to measure the voltage on thesource or grid side of switching device 160 using voltage divider 130.The voltage measured using voltage divider 130 may represent the voltage(e.g., alternating current, or AC, voltage) of a single-phase sourcepower signal being transmitted on the phase A pole of the multiple-phasepower system. Control circuit 105 is configured to measure the voltageon the load or capacitor side of switching device 160 using voltagedivider 135. The voltage measured using voltage divider 135 mayrepresent the voltage (e.g., direct current, or DC, voltage) across thecapacitor (e.g., due to the energy stored in the capacitor).

Control circuit 105 may be configured to monitor the difference betweenthe voltages on the source and load sides of switching device 160. Ifthe difference between the voltages does not approach approximately zerovolts, control circuit 105 may be configured to not generate a closesignal and switching device 160 may remain in an open configuration.When the difference between the voltages on the source and load sidesapproaches approximately zero (e.g., if the voltages are approximatelythe same), control circuit 105 may be configured to generate a closesignal and transmit the signal to switching device 160, causingswitching device 160 to close and form an electrical connection betweenthe power source and the capacitor(s). In some embodiments, controlcircuit 105 may be configured to maintain closure of the switchingdevices within +/−10 degrees of zero-crossing. Because switching device160 closes when the voltage difference between the source and load sidesis approximately zero volts, no substantial in-rush current should flowin the resulting circuit and undesirable effects of connecting to thecapacitor(s) are be reduced or avoided.

Some existing designs utilize voltage transformers to provide areference signal for proper electrical contact closure sequencing.Because voltage transformers can be configured in either phase to phaseor phase to ground wiring configurations, such variations must beaccounted for in the control scheme and configured upon setup.

By utilizing voltage dividers on both sides of switching device 160, theinstantaneous DC component of the voltage is available. Control circuit105 can use the voltage divider inputs to determine the actual voltagedifferential across switching device 160. Accordingly, control circuit105 can independently determine the voltage zero for each phase and doesnot need to have knowledge of the phase rotation (e.g., A-B-C or A-C-Bphasing) of the power system. Further, because the voltage dividers areused to determine the actual voltage on each side of switching device160 independently (e.g., as opposed to inferring the voltage on one sidebased on a measurement of the other side and knowledge of theconfiguration of the power system), control circuit 105 need not becalibrated with the specific configuration of the power system (e.g.,Delta/Wye, grounded/ungrounded, etc.) in order to determine theappropriate zero or near-zero point at which switching device 160 shouldclose. Further, no substantial in-rush current should occur as long asthe voltage differential between the two sides of switching device 160is approximately zero, even if the capacitor is still holding a charge.Accordingly, control circuit 105 does not need to wait a predeterminedamount of time (e.g., five minutes) after the capacitor has last openedbefore switching device 160 can be closed again.

In some embodiments, control circuit 105 may also be used to generatecontrol signals to cause switching device 160 to open. Currenttransducers may be used to determine an appropriate zero-current openingtime. In some embodiments, control circuit 105 may be configured togenerate an open signal without using current transducers by monitoringthe load-side voltage signal. Because the capacitors cause the currentsignal to lead the voltage signal on the load side by 90 degrees, theproper zero-current opening time may be calculated by control circuit105.

Referring now to FIG. 3, a flow diagram for a process 300 of controllingthe operation of a switching device for connecting a voltage source to aswitched capacitor according to an exemplary embodiment. In variousembodiments, process 300 may be implemented using control circuit 105 ina single phase as illustrated in FIG. 2 and/or applied to multiplephases as illustrated in FIG. 1. As illustrated in FIG. 3, process 300includes operations that may be used to control the connection of asingle phase of a power system to one or more capacitors. In someembodiments, a control circuit may be configured to utilize process 300to control each phase of a multiple-phase power system independently(e.g., such that process 300 is repeated for each phase).

The control circuit may be configured to determine a source-side voltageassociated with a power signal for a phase of a connected power systemusing a voltage signal received from a first voltage divider (operation305). The first voltage divider may be electrically connected to thesource side of a switching device for the phase. The control circuit maybe configured to determine a load-side voltage, or voltage across acapacitor connected to a second side of the switching device, usinganother voltage signal received from a second voltage divider for thephase (operation 310). The second voltage divider may be electricallyconnected to the load, or capacitor, side of the switching device forthe phase.

The control circuit may be configured to determine a voltagedifferential across the switching device for the phase using the voltagesignals from the first and second voltage dividers. The control circuitmay be configured to monitor the voltage differential to determine ifthe voltage differential is approaching approximately zero volts (e.g.,such that the source-side voltage and the load-side voltage areapproximately the same) (operation 315). If the voltage differential isnot approximately zero volts, the control circuit may continue tomonitor the voltage signals received from the voltage dividers and maynot generate a signal to cause the switching device for the phase toopen. When the voltage differential is determined to be approximatelyzero, such as when the capacitor is fully discharged and the source sidevoltage is zero, or when the same non-zero voltage is present in thesource power signal for the phase and across the capacitor, the controlcircuit may be configured to generate a close signal and transmit theclose signal to the switching device (operation 320). The switchingdevice may be configured to close and electrically connect therespective phase or pole of the power system to the capacitor(s) whenthe voltage differential across the switching device is approximatelyzero volts in response to receiving the close signal from the controlcircuit.

Referring now to FIG. 4, a single-phase schematic electrical diagram 400of a control system for controlling the operation of a switching devicefor connecting a voltage source to a switched capacitor is shownaccording to an exemplary embodiment. Electrical diagram 400 mayrepresent a high-level electrical implementation of control system 200and/or a single phase of control system 100 in some exemplaryembodiments. In some embodiments, the circuit illustrated in electricaldiagram 400 may be applied to control the connection of a voltage sourceto a switched capacitor using one or more operations of process 300.

As illustrated in electrical diagram 400, the control system includes apower source 405 (e.g., an AC voltage source, such as a high voltagepower source from a power grid) and a capacitor 410 (e.g., one or morecapacitors, such as in a capacitor bank) that are selectivelyconnectable through the use of a switching device. In some embodiments,the voltage of power source 405 may be as high as 22 kV or higher. Theswitching device includes a pair of contactors 415 that may be moved incontact with one another (e.g., in a closed position of the switchingdevice) and separated from one another (e.g., in an open position of theswitching device) to enable and disable, respectively, an electricalconnection between power source 405 and capacitor 410.

In some embodiments, one or both of contactors 415 may be operativelymoved in and out of contact with the other contactor 415 through the useof a solenoid assembly or other type of actuator. In electrical diagram400, two solenoid devices are used in conjunction with an operating rod420 to move the source-side contactor into and out of contact with theload-side (e.g., capacitor-side) contactor. A close solenoid 425 isconfigured to push operating rod 420 up, moving the source-sidecontactor into contact with the capacitor-side contactor. An opensolenoid 430 is configured to pull operating rod 420 down, moving thesource-side contactor out of contact with the capacitor-side contactor.A toggle switch 435 or other mechanism may be used to control theoperation of the solenoid devices. In some embodiments, one solenoiddevice may be used to perform both the opening and closing functions ofthe switching device. In some embodiments, a different type of actuatingdevice may be used to open and close the connection between power source405 and capacitor 410.

Electrical diagram 400 also includes two separate voltage dividers, oneelectrically connected to the source side of contactors 415 and oneelectrically connected to the capacitor side of contactors 415.Source-side voltage divider 440 includes two or more resistors and maybe used by a control circuit to determine the voltage (e.g., AC voltage)of power source 405 at any given point in time. Voltage divider 440 maybe connected in a parallel configuration with power source 405, suchthat a high voltage side of voltage divider 440 may be electricallyconnected with a high voltage side of power source 405, and a lowvoltage side of voltage divider 440 may be connected to a low voltageterminal (e.g., ground terminal, very high impedance element, etc.). Insuch a configuration, the voltage across voltage divider 440 is the sameas the voltage of power source 405.

Voltage divider 440 may include at least a first resistor 445 and asecond resistor 450. Resistor 445 may be a high voltage resistorconfigured to withstand a high voltage drop across the resistor withoutdamaging the resistor, such as a high voltage thick film resistor (e.g.,1 GΩ, 10 GΩ, 10 MΩ, etc.). Resistor 450 may be a lower voltage resistor(e.g., as compared to resistor 445) and may be configured such that thevoltage drop across resistor 450 is substantially lower than the voltagedrop across resistor 445 during operation. A control circuit may beconfigured to measure the voltage across resistor 450 (e.g., by using anelectrical connection, such as a wire lead, to a high voltage side ofresistor 450 and/or a low voltage side of resistor 450). The voltageacross resistor 450 can be used to determine the voltage across theentire voltage divider 440 because the voltage across resistor 450 isdirectly related to the total voltage based on the relative resistancevalues of resistors 445 and 450. The total voltage across voltagedivider 440 (and, accordingly, the voltage of power source 405) can bedetermined according to the following expression, where V_(VD440)represents the total voltage across voltage divider 440, R₄₄₅ and R₄₅₀represent the resistance values of resistors 445 and 450, respectively(e.g., in ohms), and V_(R450) represents the voltage measured across thesmaller resistor 450:

V _(VD440)−((R ₄₄₅ +R ₄₅₀)/R ₄₄₅)×V _(R450)

By measuring across the smaller resistor 450, the voltage may be reducedto a level that is safe for the electronics of the control circuit usedto measure the voltage value. In some embodiments, both resistors 445and 450 may be included as part of a voltage divider assembly. In someembodiments, resistor 445 may be included in a separate assembly fromresistor 450. For example, resistor 445 may be included in an assemblyconfigured to encapsulate a high voltage resistor, and resistor 450 maybe mounted or embedded on a circuit board, such as a circuit board ofthe control circuit.

A second voltage divider 455 is electrically connected to the capacitorside of the contactors 415. Capacitor-side voltage divider 455 includestwo or more resistors and may be used by the control circuit todetermine the voltage (e.g., DC voltage) across capacitor 410. Voltagedivider 455 may be connected in a parallel configuration with capacitor410, such that a high voltage side of voltage divider 455 iselectrically connected to a high voltage side of capacitor 410 and a lowvoltage side of voltage divider 455 is electrically connected to a lowvoltage terminal.

Capacitor-side voltage divider 455 may include at least a first resistor460 and a second resistor 465. Resistor 460 may be a high voltageresistor and resistor 465 may be a lower-voltage resistor (e.g.,resistor 460 might have a higher resistance value than resistor 465).The control circuit may be configured to measure the voltage across thesmaller resistor 465 and use that voltage value to determine the voltageacross the entire voltage divider 455 and, accordingly, the voltageacross capacitor 410. The voltage across voltage divider 455 may bedetermined in the same manner described above with respect to voltagedivider 445. In various embodiments, resistors 460 and/or 465 may havethe same or different resistance values as resistors 445 and 450,respectively.

Referring now to FIG. 5, a perspective view of a control system 500 thatmay be used to control the operation of switching devices forselectively connecting a three phase voltage source to switchedcapacitors is shown according to an exemplary embodiment. System 500includes three single-phase switching systems 505, one for connection toeach phase or pole of the power source. Each single-phase system 505includes a housing 510 configured to enclose a switching device used toconnect and disconnect the phase to a capacitor. The phase of the powersource may be connected at a terminal 515, and the capacitor(s) may beconnected at another terminal 520. Each single-phase system 505 includesa source-side voltage divider (not visible in FIG. 5) and acapacitor-side voltage divider 525 (e.g., an external voltage dividerelectrically connected to a capacitor or load side of the switchingdevice for the phase) that may be used to determine the voltages at eachside of the switching device for the phase. The switching devices andvoltage dividers for all three phases may be provided in one integratedcontrol system such that control system 500 is a “hook up and go” typesystem that is as easy to install as non-zero-close systems. In someembodiments, a system similar to control system 500 may be used in theimplementation of various systems and methods described herein (e.g.,systems 100 and/or 200, process 300, the electrical system illustratedin diagram 400, etc.) and control system 500 may incorporate variousfeatures described with respect to those systems and methods.

Referring now to FIG. 6, a back planar view of control system 500 ofFIG. 5 is shown according to an exemplary embodiment. In this view, apower supply input interface 605 and a control input interface 610 ofsystem 500 are shown. Control input interface 610 may be used to receivecontrol input signals to control the operation of the switching devicesfor each phase and/or to calibrate system 500. For example, a technicianmay connect a computing device to one or more terminals of control inputinterface to provide calibration values to system 500, test system 500,manually open and/or close one or more of the switching devices, etc. Insome embodiments, control input interface 610 may provide a separatecontrol input for each phase of the three phase power source.

In some embodiments, control system 500 may be calibrated once (e.g., ata factory, during production) and may not need subsequent calibration tooperate accurately once installed on a power grid node. Calibration mayinclude defining a time delay from when the control circuit provides asignal to close the switching device until the time at which thecontacts of the switching device are actually closed and in contact.Initial calibration may be accomplished by applying a voltage across thecapacitor switch source and load main terminals. The control can be putin a calibration mode and use feedback regarding the voltagedifferential across the terminals to calculate the time delay (e.g., thetime it takes from the transmission of the signal before the voltagedifferential approaches approximately zero). The time delay may bestored in the control circuit as a constant value. In some embodiments,a similar process may be used to provide a feedback to the controlcircuit during operation (e.g., for error detection and/or to makeincremental adjustments to the time delay value due to changes in theswitch response time).

Power supply input interface 605 may be used to receive operating power(e.g., 120 VAC, 50 Hz or 60 Hz, 1000 VA, etc.) for the switching devices(e.g., solenoid devices) from a power supply. Some controllers useenergy stored in capacitors to operate the solenoid or actuator in theswitch. Since capacitor energy varies with temperature, as does solenoidwinding resistance, many variables may be used to account for propertemperature compensation.

One way to provide increased repeatability and consistency is to use aconstant current power supply to power the switching devices. Solenoidsdevices, for example, have a set number of turns in their coils, and theoutput of the solenoid devices is based on the product of the number ofturns and the current applied. Using a power supply that provides aconstant current power signal to power the solenoid devices reduces thenumber and complexity of variables associated with changes incapacitance and/or solenoid winding resistance due to temperature. Insome embodiments, a pulse width modulated (PWM) current-related drivesignal may be used to compensate for coil temperature, power linevoltage and/or power line impedance variations.

Referring now to FIG. 7, a perspective view of a lateral cross-sectionof control system 500 shown in FIG. 5 is illustrated according to anexemplary embodiment. The illustrated cross-section shows a number offeatures of each single-phase system 505 that are concealed withinhousing 510. As illustrated in FIG. 7, each system 505 includes a vacuuminterrupter-type switching device. In various embodiments, other typesof switching devices may be used instead of a vacuum interrupter switch.

A switching device of system 505 includes two contactors, one for thesource side of system 505 and one for the load or capacitor side ofsystem 505. Load-side contactor 705 is electrically connected tocapacitor terminal 520 to which the one or more capacitors for the phaseare connected. Source-side contactor 710 is electrically connected topower source terminal 515 to which the respective phase of thethree-phase power source is connected. In some embodiments, source-sidecontactor 710 may be electrically connected to an operating rod 715and/or a control circuit.

Operating rod 715 is coupled (e.g., mechanically and/or electrically) tosource-side contactor 710 and is used to move source-side contactor 710into and out of contact with load-side contactor 705 to engage anddisengage, respectively, electrical connectivity between the powersource and the capacitor(s). Operating rod 715 is moved (e.g., up anddown) using an actuator 720. In some embodiments, actuator 720 mayinclude one or more solenoid devices configured to move operating rod715 and, accordingly, source-side contactor 710. In some embodiments,operating rod 715 and/or actuator 720 may be designed in a differentconfiguration and may be configured to move load-side contactor 705instead of source-side contactor 710. The operation of actuator 720 maybe controlled by a control circuit configured to determine when thecontactors should be closed and/or opened based on electrical feedbackfrom system 505 (e.g., voltage signals from voltage dividers on each ofthe load and source sides for each phase).

Referring now to FIG. 8, a front planar view of a lateral cross-sectionof control system 500 shown in FIG. 5 is illustrated according to anexemplary embodiment. Control system 500 is shown as including a controlcircuit 725 that may be used to control the operation of the switchingdevices of one or more single-phase systems 505. Control circuit 725 maybe similar to control circuit 105 shown in FIGS. 1 and 2 and mayincorporate various features described herein with respect to controlcircuit 105.

Referring now to FIG. 9, a front planar view of actuator 720 shown inFIGS. 7 and 8 is illustrated according to an exemplary embodiment.Actuator 720 includes an open solenoid device 910 configured to pulloperating rod 715 and, accordingly, source-side contactor 710 down,breaking the electrical connection between the capacitors and powersource. Actuator 720 also includes a close solenoid device 915configured to push operating rod 715 and, accordingly, source-sidecontactor 710 up, engaging contact between contactors 705 and 710 andcausing an electrical connection between the capacitors and powersource. Solenoid devices 910 and 915 may move rod 715 through the use ofa cam 905. As illustrated in FIG. 9, actuator 720 is in the openposition. In some embodiments, actuator 720 may include a singlesolenoid device configured to perform both opening and closing functionsand/or may include a different type of actuating device.

Referring now to FIG. 10, a rear planar view of actuator 720 shown inFIGS. 7 and 8 is illustrated according to an exemplary embodiment.Actuator 720 may include one or more auxiliary switches 1005. Theauxiliary switches may be configured to interrupt the flow of currentafter execution of an open operation.

Referring now to FIG. 11, a schematic illustration of an operating rod1100 that may be used in connecting and/or disconnecting a voltagesource to a switched capacitor is shown according to an exemplaryembodiment. In various embodiments, operating rod 1100 may be used inconjunction with systems 100, 200 and/or 500, in the implementation ofprocess 300, and/or as part of the electrical system illustrated indiagram 400, and may be utilized in combination with any of the variousfeatures described with reference to those systems.

Operating rod 1100 is coupled to a source-side switch contact 1155(e.g., a vacuum interrupter contact) that is movable into and out ofcontact with a load-side switch contact 1150 (e.g., a stationary vacuuminterrupter contact) through the use of a biasing mechanism 1160 (e.g.,actuator 720). Rod 1100 may be coupled to contact 1155 through the useof a mechanical adapter 1130. Mechanical adapter 1130 may be made atleast in part of conductive materials configured to transmit electricitythrough mechanical adapter 1130 without substantially impedingelectrical flow. In some embodiments, mechanical adapter 1130 mayinclude a biasing element such as a spring configured to promote a solidinterface between contacts 1150 and 1155. Source-side switch contact1155 may be electrically connected to a source terminal 1135 that isconfigured for connection to a power source, and load-side switchcontact 1150 may be electrically connected to a load terminal 1140 thatis configured for connection to one or more capacitors. Load-side switchcontact 1150 may also be connected to a voltage divider 1145 (e.g., anexternal voltage divider), and a voltage sense lead 1160 (e.g., a lowvoltage sense wire tied to voltage divider 1145) may be provided fortransmitting a load-side voltage signal from voltage divider 1145 to acontrol circuit.

Voltage sensing may be performed using capacitive coupling or using avoltage divider. Voltage dividers used to measure a terminal nearest abiasing mechanism may be created within a bushing in which the switchingdevice (e.g., vacuum interrupter) is encapsulated.

In some embodiments, at least a portion of a source-side voltage dividermay be positioned or embedded within operating rod 1100. A resistor 1120(e.g., a high voltage, thick film resistor) is embedded within operatingrod 1100 as illustrated in FIG. 11. Resistor 1120 may be electricallyconnected to contact 1155 and/or source terminal 1135 (e.g., throughmechanical adapter 1130) on a high voltage side of resistor 1120 usingan electrical lead 1115. A voltage sense lead 1110 may be connected to alow voltage side of resistor 1120 and used to provide a voltage signal(e.g., a high voltage signal for a second resistor of the voltagedivider) to a control circuit. Resistor 1120 may be enclosed within anencapsulation 1125 (e.g., a material such as urethane). Encapsulatingresistor 1120 in urethane may help provide for a dielectric capability,mechanical shock absorption, tolerance of thermal expansion, thermaldissipation, an ability to sense the voltage on the terminal nearest thebiasing mechanism 1160, and/or other benefits. In some embodiments, anouter surface 1105 of operating rod 1100 may include a rigid dielectrictube.

As illustrated, operating rod 1100 encloses only a portion, or a singleresistor, of the source-side voltage divider. The second resistor of thesource-side voltage divider may be provided elsewhere in the system,such as on a circuit board associated with a control circuit. In someembodiments, resistor 1120 may be a high-voltage resistor configured foruse with high voltages that may be experienced in a power gridapplication, and the second resistor may be a lower-voltage resistorconfigured such that the voltage sensed across the second resistor by acontrol circuit is low enough to avoid damaging the electronics of thecontrol circuit. In some embodiments, both resistors of the voltagedivider may be positioned and/or encapsulated within operating rod 1100.

The disclosure is described above with reference to drawings. Thesedrawings illustrate certain details of specific embodiments thatimplement the systems and methods and programs of the presentdisclosure. However, describing the disclosure with drawings should notbe construed as imposing on the disclosure any limitations that may bepresent in the drawings. The present disclosure contemplates methods,systems and program products on any machine-readable media foraccomplishing its operations. The embodiments of the present disclosuremay be implemented using an existing computer processor, or by a specialpurpose computer processor incorporated for this or another purpose orby a hardwired system. No claim element herein is to be construed underthe provisions of 35 U.S.C. §112, sixth paragraph, unless the element isexpressly recited using the phrase “means for.” Furthermore, no element,component or method step in the present disclosure is intended to bededicated to the public, regardless of whether the element, component ormethod step is explicitly recited in the claims.

Embodiments within the scope of the present disclosure may includeprogram products comprising machine-readable media for carrying orhaving machine-executable instructions or data structures storedthereon. Such machine-readable media can be any available media whichcan be accessed by a general purpose or special purpose computer orother machine with a processor. By way of example, such machine-readablemedia can comprise RAM, ROM, EPROM, EEPROM, CD ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium (e.g., non-transitory medium) which can be used to carry orstore desired program code in the form of machine-executableinstructions or data structures and which can be accessed by a generalpurpose or special purpose computer or other machine with a processor.Combinations of the above are also included within the scope ofmachine-readable media. Machine-executable instructions comprise, forexample, instructions and data which cause a general purpose computer,special purpose computer, or special purpose processing machine toperform a certain function or group of functions.

Embodiments of the disclosure are described in the general context ofmethod steps which may be implemented in one embodiment by a programproduct including machine-executable instructions, such as program code,for example, in the form of program modules executed by machines.Generally, program modules include routines, programs, objects,components, data structures, etc., that perform particular tasks orimplement particular abstract data types. Machine-executableinstructions, associated data structures, and program modules representexamples of program code for executing steps of the methods disclosedherein. The particular sequence of such executable instructions orassociated data structures represent examples of corresponding acts forimplementing the functions described in such steps.

An exemplary system for implementing the overall system or portions ofthe disclosure might include a general purpose computing device in theform of a computer, including a processing unit, a system memory, and asystem bus that couples various system components including the systemmemory to the processing unit. The system memory may include read onlymemory (ROM) and random access memory (RAM). The computer may alsoinclude a magnetic hard disk drive for reading from and writing to amagnetic hard disk, a magnetic disk drive for reading from or writing toa removable magnetic disk, and an optical disk drive for reading from orwriting to a removable optical disk such as a CD ROM or other opticalmedia. The drives and their associated machine-readable media providenonvolatile storage of machine-executable instructions, data structures,program modules, and other data for the computer.

It should be noted that although the flowcharts provided herein show aspecific order of method steps, it is understood that the order of thesesteps may differ from what is depicted. Also, two or more steps may beperformed concurrently or with partial concurrence. Such variation willdepend on the software and hardware systems chosen and on designerchoice. It is understood that all such variations are within the scopeof the disclosure. Likewise, software implementations of the presentdisclosure could be accomplished with standard programming techniqueswith rule based logic and other logic to accomplish the various databasesearching steps, correlation steps, comparison steps and decision steps.It should also be noted that the word “component” as used herein and inthe claims is intended to encompass implementations using one or morelines of software code, and/or hardware implementations, and/orequipment for receiving manual inputs.

The foregoing description of embodiments of the disclosure have beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the disclosure to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the disclosure. Theembodiments were chosen and described in order to explain the principalsof the disclosure and its practical application to enable one skilled inthe art to utilize the disclosure in various embodiments and withvarious modifications as are suited to the particular use contemplated.

What is claimed is:
 1. A method of controlling the connection of amultiple phase power source to a plurality of capacitors, wherein eachphase of the multiple phase power source is electrically connectable toat least one of the plurality of capacitors through a switching device,the method comprising: for each phase of the multiple phase powersource: determining a first voltage of a power signal for the respectivephase of the power source using a first voltage divider that iselectrically connected to a first terminal of the switching device forthe phase; determining a second voltage across a capacitor that iselectrically connected to a second terminal of the switching device forthe phase, wherein the second voltage is determined using a secondvoltage divider that is electrically connected to the second terminal ofthe switching device for the phase; and generating a close signalconfigured to cause the switching device for the phase to close andelectrically connect the respective phase of the power source to thecapacitor when the difference between the first voltage and the secondvoltage is approximately zero.
 2. The method of claim 1, wherein theclose signal is generated before the capacitor is fully discharged. 3.The method of claim 1, wherein the switching device comprises a rodconfigured to be moved between a first position in which the switchingdevice is in an open position and a second position in which theswitching device is in a closed position, and wherein the method furthercomprises positioning at least a portion of one of the first voltagedivider or the second voltage divider within the rod.
 4. The method ofclaim 3, wherein the portion of the voltage divider that is positionedwithin the rod comprises at least one high voltage thick film resistor.5. The method of claim 4, further comprising encapsulating the at leastone resistor within a urethane material.
 6. The method of claim 1,wherein generating the close signal configured to cause the switchingdevice for the phase to close comprises generating the close signal apredetermined time prior to when the difference between the firstvoltage and the second voltage is expected to approach approximatelyzero, wherein the predetermined time is based on a time delay between atime when the switching device receives the close signal and a time whenthe switching device comes to rest in a closed position.
 7. The methodof claim 6, wherein the time delay is determined by applying a voltageacross the first and second terminals of the switching device at a firsttime, closing the switching device, and determining a second time atwhich the voltage approaches approximately zero, wherein the time delaycomprises the difference between the first time and the second time. 8.A control system for controlling the connection of a multiple phasepower source to a plurality of capacitors, wherein each phase of themultiple phase power source is electrically connectable to at least oneof the plurality of capacitors through a switching device, the controlsystem comprising: a control circuit configured to, for each phase ofthe multiple phase power source: determine a first voltage of a powersignal for the respective phase of the power source using a firstvoltage divider that is electrically connected to a first terminal ofthe switching device for the phase; determine a second voltage across acapacitor that is electrically connected to a second terminal of theswitching device for the phase, wherein the second voltage is determinedusing a second voltage divider that is electrically connected to thesecond terminal of the switching device for the phase; and generate aclose signal configured to cause the switching device for the phase toclose and electrically connect the respective phase of the power sourceto the capacitor when the difference between the first voltage and thesecond voltage is approximately zero.
 9. The control system of claim 8,wherein the control circuit is configured to generate the close signalbefore the capacitor is fully discharged.
 10. The control system ofclaim 8, further comprising the switching device, the first voltagedivider, and the second voltage divider, wherein the switching devicecomprises a rod configured to be moved between a first position in whichthe switching device is in an open position and a second position inwhich the switching device is in a closed position, and wherein at leasta portion of one of the first voltage divider or the second voltagedivider are positioned within the rod.
 11. The control system of claim10, wherein the portion of the voltage divider that is positioned withinthe rod comprises at least one high voltage thick film resistor.
 12. Thecontrol system of claim 11, wherein the at least one resistor isencapsulated within a urethane material.
 13. The control system of claim8, wherein the control circuit is configured to generate the closesignal a predetermined time prior to when the difference between thefirst voltage and the second voltage is expected to approachapproximately zero, wherein the predetermined time is based on a timedelay between a time when the switching device receives the close signaland a time when the switching device comes to rest in a closed position.14. A control system for controlling the connection of a multiple phasepower source to a plurality of capacitors, wherein each phase of themultiple phase power source is electrically connectable to at least oneof the plurality of capacitors through a switching device, the controlsystem comprising: means for determining, for each phase of the multiplephase power source, a first voltage of a power signal for the respectivephase of the power source using a first voltage divider that iselectrically connected to a first terminal of the switching device forthe phase; means for determining, for each phase of the multiple phasepower source, a second voltage across a capacitor that is electricallyconnected to a second terminal of the switching device for the phase,wherein the second voltage is determined using a second voltage dividerthat is electrically connected to the second terminal of the switchingdevice for the phase; and means for generating, for each phase of themultiple phase power source, a close signal configured to cause theswitching device for the phase to close and electrically connect therespective phase of the power source to the capacitor when thedifference between the first voltage and the second voltage isapproximately zero.
 15. The control system of claim 14, furthercomprising the switching device, the first voltage divider, and thesecond voltage divider, wherein the switching device comprises a rodconfigured to be moved between a first position in which the switchingdevice is in an open position and a second position in which theswitching device is in a closed position, and wherein at least a portionof one of the first voltage divider or the second voltage divider arepositioned within the rod.
 16. The control system of claim 15, whereinthe portion of the voltage divider that is positioned within the rodcomprises at least one high voltage thick film resistor.
 17. The controlsystem of claim 16, wherein the at least one resistor is encapsulatedwithin a urethane material.
 18. The control system of claim 14, whereinthe means for generating is configured to generate the close signal apredetermined time prior to when the difference between the firstvoltage and the second voltage is expected to approach approximatelyzero, wherein the predetermined time is based on a time delay between atime when the switching device receives the close signal and a time whenthe switching device comes to rest in a closed position.